Did you ever think about how much you know?

Recently I met with an inventor who needed some technical help. Because I signed a non-disclosure agreement, I can't talk about the specifics of his invention. Meeting with him did bring out a lot of information that I'd forgotten that I knew. Has it happened to you yet?r

It is amazing to think about how many things have gone from being a proof-of-concept laboratory device to something that we take for granted in a few short years. Lasers is what brought this to mind. The following is not intended to be a technical dissertation, but just a few random things that I'd forgotten that I knew.

Laser used to be an acronym: Light Amplification by Stimulated Emission of Radiation. Now we don't even think about it standing for individual words. Lasers are used in CD & DVD players, printers, and even the laser pointer that you can buy very inexpensively at places like Radio Shack. The laser pointers show up as a small dot, even across relatively long distances. That's because the laser emits coherent light that isn't bothered by the air and dust particles between the source and the target. (What makes laser light coherent and what "coherent" really means is too big a topic for this discussion.)

Laser light is great for some things, such as making a small dot across the room, but doesn't work well for others. Laser light cuts through mist and fog, for example, making it a poor choice for automatically turning on a foghorn at a lighthouse. Incandescent light, such as is produced by a (now-old-fashioned) light bulb, however, bounces back and is diffused by fog. Having a light detector near, but shaded from, an incandescent light bulb would be one way to turn on a foghorn.

I'd forgotten what I knew about lasers and coherent light until the inventor and I talked. What have you forgotten that you know?r Something to think about: Just knowing what you know, plus what you could find out easily and without paying money, how would you automatically detect that enough snow had fallen over night that you would need to shovel your walk, and have something wake you up earlier in the morning than usual?r You don't need to answer, it's just a thought experiment.